It has previously been disclosed in U.S. Pat. No. 3,451,988, to Langer, to use an organolithium compound such as n-butyl lithium with a chelating bifunctional Lewis base such as tetramethyl ethylene diamine (TMEDA) as a catalyst for polymerizing ethylene and homopolymerizing or copolymerizing diolefins having increased ratios of 1,2-structure.
The present invention utilizes a catalyst system comprised of an anionic initiator based on lithium and a modifier compound which contains a lithium alkoxide and a tertiary diamine in one molecule in the form of a chelate. The present catalyst system has increased stability at higher temperatures than does the prior art catalyst systems which employ chelated diamines. This increased stability allows for more economical production of homopolymers and copolymers of medium-vinyl diolefins at higher polymerization temperatures.